Developmental disorders such as autism offer a unique opportunity to identify important brain structures and functional circuits that underlie complex, perceptual, cognitive, and social behaviors. The proposed multi-disciplinary program, utilizing behavioral testing (Project I) and MRI spectroscopy in autistic children (Project II), and behavioral, MRI-spectroscopic, and neuroanatomical studies in monkeys (Projects II and III), offers a comprehensive analysis of testable animal model of human autism. According to this hypothesis, early damage to the amygdala-orbitofrontal circuit causes a developmental impairment characterized by disturbances in social, emotional, and cognitive behavior. Project IV will evaluate the degree to which the infant responds to injury to the orbitofrontal-amygdala circuit. In order to evaluate fully the possible mechanisms of functional reorganization following this neonatal brain damage, the normal infant and normal adult patterns of cortico-limbic connections will be evaluated using modern neuroanatomical pathways tracing techniques. These patterns of connections will then be correlated with the immunocytochemical development of this circuit and closely related structures. Next, the patterns of cortico-limbic connections with be evaluated in adult monkeys that received either early or late lesions of the amygdala or orbitofrontal cortex. These results will establish the degree to which the developing nervous system can utilize compensatory mechanisms to stabilize developmentally transient neural pathways, to recruit new pathways between weakly associated structures, or to recruit new target structures into functional cortico-limbic circuits. Overall, this research will make a significant contribution towards our understanding of the neurobiological bases of pervasive developmental disorders.